Over the past few years substantial progress has been made in developing operable techniques for separation of various isotopes by laser induced processes. R. V. Ambartzumian, et al., describe a laser isotope separation process in a paper entitled "Sulfur Isotope Separation With An Enrichment Factor&gt;10.sup.3 Caused By Irradiation Of SF.sub.6 Molecule By CO.sub.2 Laser", which appeared in JETP 21, 375(1975) on Mar. 20, 1975. In this article it is taught that SFhd 6 can be isotope-selectively dissociated by a CO.sub.2 laser at a power density of from 1-2.times.10.sup.9 watts per cm.sup.2 with the laser tuned to the P(16) laser line (948 cm.sup.-1). Since that time it has been found that substantially lower power density can be employed. It should be noted that while the Ambartzumian, et al., article refers to SF.sub.6, many other laser isotope separation processes have been developed over the last few years including ones for separating isotopes of uranium from gaseous compounds.
The Ambartzumian, et al., article discusses the photo-dissociation in a static cell. The static cell is a batch process which is not inherently suitable for large scale processing. One problem with batch processing in a static cell is that the amount of separative work done by each successive laser pulse decreases since the absorption characteristics of the gas in the cell is inherently altered from pulse to pulse by the dissociation process. Therefore it would be necessary to either accept the reduced efficiency or have a complex system for readjusting the laser to maintain efficiency. It should further be noted that another consequence of the depletion of the sample within the cell is that the material being acted upon with each successive pulse is less enriched and therefore less susceptible to efficient separation.
U.S. Pat. No. 3,443,087, which issued May 6, 1969 to J. Robieux, et al, entitled "Isotopic Separation Process", suggests an interconnection of several stages of isotope separation according to the methods of fractional purification with reprocessing of the gas streams provided thereby. This process requires separate lasers for each cell. The absorption characteristics of the gas within each of these cells is different, thereby requiring a different adjustment for each laser. This system also suffers from the deficiency that to the extent that the gas within each cell is subject to more than one laser pulse the absorption characteristics within that cell vary from pulse to pulse.
Therefore, it is an object of this invention to provide a method and apparatus for the separation of isotopes by a laser in which either multiple laser pulses or continuous wave radiation can be employed to efficiently separate isotopes without affecting the absorption characteristics of the isotopes mixture being operated upon.